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OS/pintos-env/pintos/examples/lineup.c

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/* lineup.c
Converts a file to uppercase in-place.
Incidentally, another way to do this while avoiding the seeks
would be to open the input file, then remove() it and reopen
it under another handle. Because of Unix deletion semantics
this works fine. */
#include <ctype.h>
#include <stdio.h>
#include <syscall.h>
int
main (int argc, char *argv[])
{
char buf[1024];
int handle;
if (argc != 2)
exit (1);
handle = open (argv[1]);
if (handle < 0)
exit (2);
for (;;)
{
int n, i;
n = read (handle, buf, sizeof buf);
if (n <= 0)
break;
for (i = 0; i < n; i++)
buf[i] = toupper ((unsigned char) buf[i]);
seek (handle, tell (handle) - n);
if (write (handle, buf, n) != n)
printf ("write failed\n");
}
close (handle);
return EXIT_SUCCESS;
}